I. Field of the Invention
The present invention relates to methods for preparing food products, and in particular, relates to methods for canning citrus segments or membranes containing citrus sections, such as grapefruit.
II. Description of the Prior Art
Citrus fruit products are made commercially available in numerous forms, including fresh, canned and concentrated juice; fresh whole fruit; as well as both glass packed and canned fruit sections. Citrus sections as well as other processed citrus products are available in different container sizes.
In the preparation of citrus fruit sections for canning, it is first necessary to remove the outer skin or peel. This may be done in a conventional manner by heating, mechanically or by hand removing the peel followed by a lye bath and water rinse.
Citrus fruits, notably oranges and grapefruit, have a membrane separating adjacent fruit sections. In the case of grapefruit, this membrane is quite tough, having a strength of about twenty-five (25) ounces (measured by cross sectional stress on the membrane by an Altek Tensil Tester). To render the fruit sections palatable, the fruit sections must be separated, usually by hand, or by a machine to remove the sections from the membrane. This process is quite labor-intensive with a low yield, which increases production costs. A good description of the sectionizing process is set forth in the United States Department of Agriculture Handbook entitled "Chemistry and Technology of Citrus, Citrus Products, and By-Products", Agriculture Handbook No. 98, revised 1962, in particular see pages 30-33.
Further, the United States Department of Agriculture has established certain standards and grades for canned and bottled citrus fruit. See, for example, "United States Standards for Grades of Canned Grapefruit" 6th Issue, effective Oct. 25, 1973, established by the U.S. Department of Agriculture, Agricultural Marketing Service, Fruit and Vegetable Division (Processed Products Standardization and Inspection Branch); and see, "United States Standards for Grades of Canned Grapefruit and Orange for Salad", Third Issue, effective Apr. 8, 1975, U.S. Department of Agriculture, Agricultural Marketing Service. The hand sectioning method described above tends to render the fruit sections non-uniform in addition to increasing the overall costs of the finished product. Further, in the case of grapefruit, the physical handling of the fruit during the removal of the sections from the membrane tends to destroy the juice sacs, thus rendering an end product which is very fragile.
In U.S. Pat. No. 3,396,040 (now U.S. Pat. No. Re. 27646), Cohen discloses a process for preserving citrus fruit products by pressure cooking after the fruit has been sectionized and placed in a glass container.
Other prior art of interest includes the following:
U.S. Pat. No. 2,930,706 to Moulton; a phamplet entitled "By-Products and Speciality Products of Florida Citrus", by J. W. Kesterson, et al, from the Agricultural Research and Education Center, Lake Alfred, Florida; a book entitled Commercial Fruit and Vegetable Products, by W. D. Cruess, 3rd Edition, 1948, McGraw-Hill Book Co., Inc., New York.
In the canning of citrus sections as described above, it is conventional to elevate the center can temperature to about 168.degree.-171.degree. F. in order to preserve the fruit.